Sinn Fein leader Gerry Adams claimed he has become the victim of a witch hunt over allegations that he covered up his brother's sex abuse.

The Louth TD, who is facing mounting criticism over his handling of the controversial case, has accused political opponents and the media of attempting to bring him down.

"I have committed no offence," he said.

Earlier this month Adams' younger brother Liam was convicted of raping and sexually assaulting his daughter Aine over a six year period from 1977 to 1983 when she was aged between four and nine-years-old.

Questions were raised after it emerged during the two-week trial at Belfast Crown Court that the republican stalwart had known about the abuse but had not told police for nine years as his niece went public with the allegations in a television documentary in 2009.

There was also criticism that Liam Adams was allowed to work with children in west Belfast and Dundalk, Co Louth.

Defending his stance the former West Belfast MP said that police and social services had known about his abuser brother since 1987 but failed to act.

He also claimed he had tried to facilitate a meeting between his niece and brother years later because Aine had wanted an acknowledgement of guilt from her father.

"It was not my place to take decisions for her or to take any actions, other than what she wanted at the time which was for Liam to acknowledge that he had sexually abused her," he said.

This week the Northern Ireland Police Ombudsman Dr Michael Maguire confirmed his office had launched a formal investigation to establish whether or not detectives properly examined if Mr Adams hid the crimes of his paedophile brother.

The region's Public Prosecution Service and Attorney General are also looking at the case alongside the Police Service of Northern Ireland.

Mr Adams said: "Four law agencies in the north are now investigating or reviewing aspects of this case, mostly in respect of my evidence.

"This is unprecedented. I have learned of all of these developments in the media.

"My rights, if I have any, are unclear.

"I think in the interests of fairness that those sections of the media and those politicians who have been involved in a quite despicable campaign in recent days should allow these agencies to complete their work."

In April, Mr Adams appeared as a prosecution witness during a trial against his brother. At that time it was revealed that Liam Adams had confessed to the abuse during a walk in the rain in Dundalk with his older brother in 2000.

The trial subsequently collapsed because of legal reasons and when it resumed again last month, a senior prosecutor revealed Mr Adams would not be called.

"I co-operated fully with the PSNI," he said. "I made statements in support of Aine.

"I co-operated fully with the Public Prosecution Service and with the prosecution lawyers.

"I gave evidence in court against my brother and in support of Aine.

"I reject unconditionally the charge that I committed any offence. I did my best and continue to do my best to deal with this issue."

Branding the accusations of a cover-up as "patently cynical and untrue", the republican veteran, who has also revealed his father Gerry Snr subjected some of his children to physical, sexual and mental abuse, claimed his family were now struggling to cope.

He added: "All of this has been hugely testing and challenging for me and for my clan. Only those who have had to go through this can appreciate the trauma it has caused.

"I am a public figure and subject to scrutiny and that is fair enough - but the despicable manner in which this issue is being dealt with by the DUP and others, and by some cynical elements of the media has become trial by media and a witch hunt."

Mr Adams appealed for his extended family to be given space and privacy.

He said: "My extended family have all been affected by this case. I am not asking for the media to give me some special dispensation. But my family should be given the space and privacy to heal the hurt."